Silicon magnetic sensors mainly include Hall sensors, AMR sensors, and GMR sensors. With respect to the Hall sensor, a semiconductor film, such as indium telluride, is deposited on a substrate and the path of a carriers is deflected by an external magnetic field in order to provide different resistances. The advantage thereof is the Hall sensor can measure a relatively wide range of magnetic fields, but a disadvantage thereof is the sensor has low magnetic field sensitivity, and it is generally necessary to introduce a flux concentrator to amplify an external magnetic field. With respect to AMR sensors, a single-layer magnetic film is deposited on a substrate, and the magnetic moment direction of the magnetic film is changed in response to an external magnetic field, thus changing the resistance measured across the ends. Sensor units and electrodes thereof patterned into a slanted bar shape, such that a desired angle is formed between the current direction and the magnetic field direction, when doing so the magnetic field direction can be detected. The advantage is the sensor units are simple and only have one layer of film, but a disadvantage is the sensor has a relatively low magnetoresistance and thus poor sensitivity. A GMR multi-layer film magnetic sensor is a magnetoresistive sensor formed by a nanometer-thick multi-layer film structure composed of ferromagnetic films and conductive films, which changes the resistance in response to a relative change of the magnetization direction of the magnetic film layers producing a change in the path that the electric carrier must travel through the magnetic field when the carrier passes through the multi-layer film. This provides a further improvement in magnetoresistive relative to an AMR sensor.
Compared with the above technology, a TMR sensor changes the relative percentage of up/down electron spins introduced in the ferromagnetic layers respectively, these layers are a ferromagnetic pinned layer, separated by a non-metallic insulating layer, from the ferromagnetic free layer, and by designing the free layer such that the magnetization direction of the free layer moves proportionally in response to an external magnetic field. Then the current that tunnels between the ferromagnetic free layer and the reference layer changes, resulting in a change of resistance of the sensor. The magnetoresistive change magnitude thereof may exceed 200%, which is much higher than that of the Hall, AMR or GMR type magnetoresistive sensor.
At present, silicon magnetic three-axis linear magnetoresistive sensors are widely used in consumer electronics, for example, mobile phones, tablet computers, and other electronic products. A three-axis linear magnetoresistive sensor includes an X-axis linear magnetoresistive sensor, a Y-axis linear magnetoresistive sensor, and a Z-axis linear magnetoresistive sensor. These sensors are mostly Hall, AMR or GMR sensors.
Therefore, in order to expand the application field and range of TMR magnetoresistive sensors, the present invention proposes a single-chip high-magnetic-field X-axis linear magnetoresistive sensor with a calibration and an initialization coil, which has excellent linear range and magnetic field sensitivity, and is fully qualified as a replacement of the present Hall, AMR, or GMR type X-axis linear magnetoresistive sensor.